you wont find silicone resin bud!
silicone is what you need for the molding
resin is what you need for casting.

the whole process is relatively simple but the materials are key!
the more your willing to invest in materials the better the finished results will be.
this takes time to perfect and can be exspensive when you first start as you will always make mistakes to start with and this wastes a lot of material.
you will also need to put a lot of thought into every mold you want to create as every item you want to copy is different from the next and certain items will require different molding tecniques.
any hobbycraft or model shop that sells railway stuff will have all the basic stuff needed to get you started.
if there is something specific you have you wont to copy pm me and the next time i mold i will do it for you.
someone else also asked a while ago of i could do some bits for them but i cant remember who so let me know!