My SP 101 wears Hogues. I found the speed loader cutout on the originals burised the inside of my firing hand's thumb when firing full throttle 158's. The Hogues resolved the issue. I have a hammer spur but find I can group as good using DA with mine. That surprised me. I was previously carrying a .38 Mod 60 for years and shot it best SA (and as quickly as most shoot DA). But the SP 101 has a great DA trigger, stacks a little and works out great.
I tried an Uncle Mikes IWB open top over my appendix like I used with the Mod 60, but with the greater grip length and my build, the grips printed a bit with pull over shirts. I have since quit using a holster. I wear a 2" leather belt and just drop the revolver inside my britches and the grips snuggle in between my belly and belt and stay put. I've never had the revolver slip, even when running chasing after my Jack Russel terriers, climbing, working under vehicles, wading streams etc...
I do occasionally use the IWB holster as a shoulder holster in a homemade rig. I use a small cotton blend web belt from a mil surplus store buckled around my chest. I sewed a second piece of belting to make a loop over my shoulder to help control the belt around my chest. The open top IWB then tucks right in under my arm and the SP 101 stays put very well. Works great with dress shirts.
I also carry 1 HKS speed loader with 5 spare rounds in my left pants pocket.