As @devicex has learned, I’ve been using 60 mm travel sliders for Kosmo modules.
They’re the longest ones Tayda sells. Mostly $1.69. They also have 30 mm, a few 20 mm, and exactly one 45 mm. Made by Alpha.
Mouser (US site) lists a number of 100 mm sliders available in single units starting at $4.67. If I go to their site, go to passives → pots → slide pots, then filter on 100 mm and “in stock”, there are 26 results with the best selection being the PS100 series from BI Technologies (6 results) and PTB series from Bourns (4 results).