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.
For example:
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.
