If they get ruined by being wet IMO they`re a very bad motorcycle glove that does`nt deserve the name! They`ll get wet if you get caught in the rain anyway so if you can`t return the for a bigger size wear them & immerse them in some warm water for a while until sodden. Squeeze the excess water out & allow them to dry naturally, not on a radiator etc, then apply your favourite leather conditioner
It isn`t guaranteed to make a massive difference but it might help a bit