I ended up buying a Marshal excelsior MEGR-295P. Its rated for 175,000 btu, and from what I can find, the one installed is 165,000ish but. It should just be a 1:1 swap. It's seemingly a good middle ground in price and quality. Some of the once I found for sale look like junk and have reviews to support that.
I really would have preferred a higher flowing one just because they seem built better, but time is of the essence, and they wouldn't arrive until next week. This M.B. Strugis brand seems bomb-proof and offers 400,000 but output if necessary. Maybe next time I can see this coming before it happens, and order one of those instead.
An other option would be buy the MB Strugis and install when she gets home and save the replacement as a backup. Guess the Blackstone uses a lot of gas