I'm not sure where you should advertise, but I might be able to do some testing for you. I am the senior accessibility tester for a university and I occasionally do consulting jobs as side gigs. If your interested in talking details PM me and I will give you an email address. FIY, I'm probably not going to have any time for new projects until after July 11th, but an opening could come up before then.

Good luck,

If it’s payed, you can send me a message, I do some of that and know a few others who do as well.

Please feel free to pm me if you need paid accessibility testers. I test websites with the mainstream screen readers on Windows, plus ios and mac. While looking online is a good short term solution, your company may want to hire an accessibility tester on either a full time or consultant basis.
Hope this helps and I'd be glad to answer any questions you may have.