Substitute for ground crayfish?
You might give shrimp-based things a shot. If you have any kind of Asian grocery store around, you can probably find dried shrimp, shrimp paste, or even shrimp powder or bullion. You might find some of these things in Mexican grocery stores too, and shrimp broth-related stuff is sometimes sold in Western grocery stores too.

You could also try other seafood-based condiments. For example, furikake comes in a lot of varieties, including some with shrimp (ebi) or fish (bonito). There are likely to be some Asian liquid sauces that you'd like too, though I'm not sure what to specifically recommend there.