Two options for DIY collimating cap...
Film canister - go to a camera shop & ask if they have any... I got some this way but, I drill holes in them & use them as caps desicant in my guide scope focuser.
Find/purchase a 1.25" focuser cap... they have a flat top with three curved sections that fit in the tube... the slots between the curves are where the grub screw sits... this is what I use although, I have a Cheshire too... & a laser...😊
I like the cap for quick checks...
If you purchase a Cheshire, have a look on eBay... doesn't need to be a branded one... think I paid like $15 for mine... works just as well as a $75 Orion one just quietly...
Cheers