Avgas is expensive, and not the best fuel for a Rotax, but so far as I know all Rotax engines can be run on Avgas.
A trick I've used a few times is to trickle the oil into the filter funnel as I carefully refuel from an Avgas pump - it works well enough.
The other obvious trick, is to take a 20 litre jerry can with you (easy enough if flying solo in a 2-seater at-least) ! Flexwings generally don't like being too light from a handling viewpoint, so one of those - full - in the back seat is a good thing from numerous viewpoints.
G