I just finished the journey you are currently on.
Decide on what type of shots you want. If you just need product shots, a 50mm is fine. Trying to get bugs with a 50mm will ensure you scare them away because you are so close.
You could go for a 200mm, and get GREAT bug shots, but they cost an arm and a leg.
So that leaves the 90-105mm range. And from my research, there are only 2 real choices here for build and quality; the Sony 100mm or the Tamron 90mm. Not super cheap, but you get what you pay for in glass.
I was exploring the used market on some great Minolta glass and would have easily bought one, but nothing was on the market in the short time I needed to make the purchase.
I ended-up buying the Sony 100mm and am quite happy with it.
Happy hunting.
Cheers!