Depending on how daring you are, you can "convert" H4 to H4h...kind of (the element will still be different).

The best method I've seen so far is to cut the base with tin snips so that you have the 3 long prongs. Then bend them so that the bulb will sit at the same depth as the H4h. On some headlights, this can dramatically improve lighting vs just using H4's in there.

There are other ways of doing this including cutting and soldering, etc...

Good luck.