Dwarves of The Last Alliance

[Kuruharan]

maybe the dwarves didn't fight at Dagorlad

No dice. Dwarves are specifically mentioned as having fought there.

All living things were divided in that day, and some of every kind, even of beasts and birds, were found in either hose, save the Elves only. They alone were undivided and followed Gil-galad. Of the Dwarves few fought upon either side; but the kindred of Durin of Moria fought against Sauron.
-Of the Rings of Power and the Third Age

Since Dagorlad was the great battle of the age we have to assume that the dwarves fought there.

Really people, I think you are making this much harder than it has to be. Tolkien specifically stated that the dwarves laid their dead in stone. He gives us the one exception to this rule and emphasizes its uniqueness. There isn't any mention of dwarven corpses in the Dead Marshes. We have to assume that the dwarves found some means of honoring their burial traditions whether they shipped the bodies back home for burial or buried them in the Mountains of Mordor.

I would suggest that perhaps the number of dwarven slain was possibly so small as to render either method relatively easy...except it is very difficult to get a grip on the number of possible participants in this war. The armies on both sides were obviously very large, so the Longbeards could potentially have sent as many as 10,000 warriors and this could have been accounted "few" in comparison with the numbers of men and elves in the army (although this is perhaps an extreme example to illustrate the problems in the question).