You probably can use a lower amp rated switch for block control. The amp rating is for making a contact and not just holding. I use 3 amp rated mini push button switches for over 44 years and they hold about 6 amps when running just fine. I normally do not work a block switch with the fully loaded loco running on the block.
Ebay is good source for small electronic items and most come from that power house country, China.
Charlie