Recently needed a drive belt for a Roco German HO engine and to fix a stem leak in the bathroom. Rather than drive all around town at $4.00 per gallon i gave Ebay a shot. Doing a search for metric o ring the cheapest with shipping i found a guy in Florida selling o rings for paintball guns. Free shipping and you can order thes size you need. Measured everything in the house i needed and ordered a bunch. Not only fixed the Roco but got spares for the Athearn old drives and tires for the Mantua engines. Every o ring came marked in a plastic bag with the size. Great service. Just thought this might help soneone out.
Bob