Thanks, everyone, for your insights. To make a long story short, late yesterday (Friday) afternoon, I got an appointment with the ostomy nurse at Cleveland Clinic (where my surgery will take place 3/20, and which is two hours from where I live) for 3/9 for patch testing specifically related to ostomy products. Though the timing is very tight, they will at least get a preliminary reading on the patch testing during pre-op on 3/13, which will help me make a final decision on 3/16 or 3/17 about which urinary diversion to have done.

Prior to getting that appointment, I requested sample materials from various producers, but they won't arrive till late next week, and they won't represent the full spectrum of possibilities. I saw a dermatologist who knew virtually nothing about ostomies and related skin issues but referred me to an allergist, hoping for an appointment early next week. But the allergist needs me to bring the full range of possible products in to create a custom patch test, and I can't acquire those on time for the appointment. The local hospital wound care department is unwilling to give me any sample materials until I have an intake appointment with them, which can't happen till the end of next week.

Given all that, I think the patch test with Cleveland Clinic on 3/9 is my best bet. Thanks again for your input!