I have a friend who is a nurse, I asked him about sterile stuff, and he pointed out that Amazon absolutely sells what is needed. Funny part about that is next time we visited he dropped off a bag full of syringes, needles and syringe filling tips. Way more than I would ever need. Anyway, I will share some stuff here with you.

IM is clean, it's easy and you can do it yourself. Don't compare it to IV use because it just is not the same nor are you going to keep doing this or be compelled to. It is also the most precise way to dose yourself.

https://m.psychonautwiki.org/wiki/Volumetric_liquid_dosing

All you need:

https://www.amazon.com/2inch-Industrial-Measuring-Individually-Sealed/dp/B09ZLJXK3T/