I had a heck of a job finding kits in 1/48th scale, as all versions are currently out of production.
I finally got the re-released late-model H-22 with the V-1, to convert back to a H-4, using the Squadron/Falconvax dorsal canopy, and trimming the prop blades, I then managed to win a H-4/H-6 version on e-bay, at a reasonable price (having lost one imported from Canada, due to HM Custom!), which will be made into a H-2.
Note that these Revell / Monogram kits are all the same basic mouldings, with parts relevant to the model type. The exhausts in the H-22 are right for an earlier H-2 to early H-4, but those in the H4 kit are later type, used on some late H-4s and then the H-5.
You might be lucky with prices, but be prepared to pay a lot for the H4 version - the H-22 gets re-released about every two years, and is priced much lower at retail price, and I would think the H4 will be re-released at some time too.