I only selling transparent stickers for 3x3x3 cube. And it is not a good selling product, so I do not offer this kind of stickers in my shop, but I can help a bit:
There are some suppliers who sell transparent vinyl rolls. They are a bit higher in price than a normal stickers, but available. You can cut them with plotter, or by hand.
Avery 4500 TF
(But of course there are other brands as well)
On this image you can't see it is transparent, because they put a background foil on this sample for easier color recognition, but when you apply, you can see trough them.