I hear ya' about every year the trips getting a little harder. Don't put it off - you'll find something. There have been times that I have been sure I would never find what I needed in an accommodation for a specific traveling companion(s) and I just looked harder LOL and have always found something. Sometimes you have to compromise a little on what you wanted.
I will second checking with Guest Apartment Services - they're great. You never know, they might have something that would work. If you've not heard of Haven, I'd check them too.
Since you're saying you're "hoping to ..." I am assuming that you've not booked flights and that your dates are somewhat flexible. If you're just checking websites for availability, I wouldn't rely on that. I have found in the past if I am looking for something specific for a stay it is best to directly email the vacation apartment rental agencies with exactly what I am looking for (like, must have a lift, must have stand-up shower (not the hand-held in a tub), etc. Mention if your dates are set in stone or how flexible they are. They know their inventory and can throw some alternate suggestions at you that you might not have considered (refer back to "sometimes you have to compromise a little").
If in the end you really can't find an apartment to suit, you can consider hotel options. Like this place -- I have never stayed here but I know exactly where it is and the location is very central and convenient for walking almost everywhere. They have suites, junior suites and an apartment (adjoining suites) with kitchenettes. https://www.hotelresidencedesartsparis.com
I've not stayed at these either, but have made note of them for future possibilites as they've been mentioned on forums as having suites or kitchenettes etc...
https://www.leprinceregent.com/
https://residence-charles-floquet.fr/
https://www.apartmentsdulouvre.com/