The only appraisers I've been able to find that in this space are Charitable Solutions and Crypto Appraisers. They do qualified appraisals of Bitcoin and other common cryptocurrencies in addition to Ethereum.
You could try searching around for an appraiser at any of the major appraiser
associations, but there don't seem to be any results for cryptocurrencies (as of date) so you'd have to start asking general property or business appraisers if they'd be interested in branching out a bit. Also, in my experience most of the time the fees will be in the upper hundreds, if not over a thousand, for even the most basic appraisal.
Still, given that Ethereum is up around 900% over the last year, the tax savings could be significant (thousands of dollars).
Probably well worth several hundred bucks and a little hassle.