Rick,  Having recently purchased a Wilesco model steam powered workshop
(model D141) on-line I can give you at least one source for Esbit dry
fuel pellets on-line.  Kenny McAtee sells Wilesco and other model steam
engines and supplies and can be emailed at <kmcatee@insightbb.com>.
I found him helpful and knowledgeable.

Happy steaming.

Marc J. Sachnoff