I've not seen Colombian Ramshorn, but you're aware that they eat plants, right? They even eat other snails.
Regarding MTS, your nearest aquarist should have some, or your nearest petshop. Basically they're extremely common. They don't eat plants and are great at scavenging leftover fish food, but do eat fish-eggs, so if you're going to breed egg-laying fish you don't want these guys in there.
If you can't find any locally, email me and I'll mail you a dozen, though I'm not sure they'll reach you alive.