you might want to try which is to put one of the orange o rings around one and then insert it into the stem
The problem will be taking the capsule out of the stem. You will have to push it from the other end or let the capsule protrude enough to be able to grab it to take it out (in this case you'll also have to be careful when I setting the stem in the chamber).
Personally I find the sucking method of loading so easy that TBH I wonder how the capsuals are any easier or more discrete
Each time I straw suck herbs in my TM stem I get weird looks from people around, even friends. Dropping a prefilled capsule into the chamber is more discreet and it's also a bit easier especially if there is wind outside.
Those little capsules also smell less than an open little container of ground herbs and no one can see the herbs.
For on the go use do you just use a stash jar or something for the ground herb and suck it up from there
I also do this most of the time but use the capsules if I really need more discretion (crowded public places like train stations for exemple, or when I'm inside and use my smokebuddy).
I tried the capsule without lid and it works well. I could put the capsule open end facing the heater with the load just temped enough the nothing spilled out of the capsule even though I just dropped the capsule in the chamber (with a bit of care). The smoother, gentler solution would be having the stem in hand (mouth side down), puting the capsule on it, open side up, and sliding the TM on the stem+capsule. This way nothing can spill.
I also tried putting the capsule open side up and the stem sitting on it. I ended up having that capsule load partially sucked into the stem and it maid quite a mess when took that capsule out of (Nothing that can't be arranged by a good blow though).