Perhaps use another sheet protector as a page divider, but add a sheet of card stock [or trim a manila folder to slide in, to give it body], then use separate, self-adhesive divider tabs onto that divider page you made from another sheet protector. Here's what I got back upon using a search engine, but there are numerous brand names and sources to choose from:

Avery Self-Adhesive Index Tabs w/Printable Inserts - Self-Adhesive Tabs W/Laser Printable Inserts, 1-1/2"L, Asst
Item # 1118212