I know of a swedish shop selling a french produced RTV silicone. Check www.kinn. com, -gjutning,-silikon.
I've ordered a kilo of the -181 stuff, did 3 12cmx 7cmx2cm molds, have more than half of it left and paid 360 svenska kronor. The molds came out nicely, imo, but i can't say anything about durability,yet. Delivery might take a while, the shop has just opened up. MvH till Norge.