You are maybe 2 if not 3 years tardy to the pardy. Rarely many advertised on San Antonio eccie, but if you cruise CL or BP you will find multiples listed. Some may be female; many more likely TS.
And if you search (here) in Houston and maybe some other larger cities, gloryholes abound.
Used to be, still is/are several ladies in SA who have offered glory hole services, sometimes it was the provider advertising herself, sometimes her gal pal or sometimes another "friend."
BTW,cardboard is so "cheap!" And imo if you hit the sides, scratch!
Last promo I recall was with a sheet dividing a room.