Incontinence: Cleaning Wheelchair. Any recommendations?

Can you wheel the wheelchair into the shower and give it a good clean with a brush and 409 or some other powerful cleaner?

Put chux pads under her.

A lot depends on what kind of wheelchair seat you have.
First, are you certain the seat cover doesn't come off?
If not I would treat this like any other upholstered chair, try an enzyme cleaner meant for pets like nature's miracle stain and odour remover, if you have access to a steam vacuum or just a shop vac you can use that to suck up any excess solution.

And definitely use washable or disposable pads to keep this from recurring.

I recommend you consult the manufacturer. You should be able to find contact information on the wheelchair itself, or possibly on labels stitched to the seating.

Put chux under her so you won't have to keep cleaning the seat.

https://www.amazon.com/s?k=chux+pads&gclid=EAIaIQobChMI-vqWsf3j9AIVE25vBB3r6gWcEAAYAiAAEgIYbfD_BwE&hvadid=153740473345&hvdev=c&hvlocphy=9019596&hvnetw=g&hvqmt=e&hvrand=5277696063792157259&hvtargid=kwd-1131733668&hydadcr=3059_9553178&tag=googhydr-20&ref=pd_sl_54d5ydtpwx_e

albedo: Imho, perhaps the manufacturer of the wheelchair, which will be located on the item, will provide information on how to clean and/or replace its seat.

This one I can help with!
There are several good cleaning/odor control on Amazon. I use Odoban - it works very well, and is used in institutional settings. I also use it in my laundry, on floors, etc.
I got a good wheelchair seat pad with a removable, washable cover. The gel pad can be cleaned (and try wrapping it in a thick trash compactor type trash bag), and the cover popped in the washer. It also makes the chair much more comfortable for the user! You might also try putting a soft bath towel
over the seat. Good luck!

Once the chair is scrubbed and disinfected, place two or three layers of plastic onto the seat of the wheelchair to protect the seat. Then place two or three towels over that to catch the "stuff". Or get a good gel seat with a washable cover over it. Put that down and put plastic over that as well and then a towel. What a terrible situation. Why is she in your home and not a facility? Please clarify this for me. And maybe she should be put into the bathroom more often.

You need "chux" disposable pads for anywhere she sits. Double up if necessary.
These are cheaper than the puppy pads someone recommended.
I also have several washable large cotton pads with a vinyl backing for bed or recliner.
I found all products at Amazon.

There are some things you can do. First, make sure that well fitting, adult pull up diapers are being used for your wife. Take any antibacterial liquid soap, I recommend Dial, apply on cloth and work up a suds using very warm water. With disposable gloves on, scrub seat in circular motion, allow suds to remain on seat a few minutes then wipe off residue with another wet cloth. Repeat at least twice. Allow to dry as much as possible. Clorox makes a fabric sanitizer spray that can be found in grocery store or Lowe's hardware. Put a plastic backed sheet pad on seat that can be changed frequently, found at pharmacies, or you can use the small pet pads. When chair is not in use, reapply a light spray of sanitizer. Most important is insuring your wife's diaper is changed frequently to avoid leakage, urinary tract infections, and skin irritation. If the cleaning does not improve the situation, contact Medicare and inquire if you can get a replacement, vinyl seat. I'm curious why she has a "rented" chair as with Medicare, she is entitled to one with doctor written order.

First try paste of baking soda and vinegar…let sit for an hour, then wipe off. Second try Shout or Dawn dish soap to remove stain. See if seat cover can be removed and either washed in machine or replaced. If you replace it, then always use the Chux/seat pads and definitely make sure diapers are fitted correctly.