All the info I had gotten at that point had come from my independent research and measurements of the LC's firewall and the booster in hand. But now I have found a good source, which I linked above. I know it's not the only resource, but hopefully that can help someone.
Thanks for the insight on VSC. What web page are you referencing?
EDIT: I found this site, input my VIN, and came up with this part, which I promptly ordered.
https://www.toyotapartsdeal.com/oem/toyota~brake~booster~assy~w~master~cylinder~47050-60010.html
Good morning! In my efforts to put my 02/1999 Elsie back on the road, I sourced a brake booster assembly to replace the bad one I took out 3-4 years ago, and even though it was for a "1999", it doesn't fit the bolt pattern on the firewall. The replacement booster has a bolt pattern of...