Sorry that you're having trouble sourcing your materials. I can usually get everything that I need in about a week; two at the absolute max. But....... unfortunately.......I am familiar with the back-order thing!
You can use the Partridge Bartleet CS10/1 hook in a #6; the same as for the Grub pattern, and you'll be just fine. The Haretron dubbing is just what I'm using, but any spikey dubbing in tan to lt. brown will work well for you. You won't need the leech yarn for the March Brown pattern. So, you may have what you need for this pattern already.
But, if you can't source something, then post again and I'll go hunting for you.
I'm glad that you liked the Grub patterns; they were a lot of fun to tie up; recipes are all in the Appendix at the back of Tom's book.