What are you using now?
I use a food sieve from the dollar store, a wire fruit basket that has very fine holes. I have two English riddles, one has 1/4" holes and the other has 1/8" holes. Billie

I am using wire with a wooden frame around it so that it fits over a container. The wire holes are a little to large. I thought about a sieve. Do you just sit it on something or put it over a container?

The sieve from the dollar store fits in the top of a standard bucket. 2 gallon?? The riddles fit in the top of a 5 gallon pail.
Years ago I had a wooden frame sieve but it was so heavy and big that it was hard to take with me for teaching classes. I found my first wire fruit basket with about 1/8" openings at a thrift store. Billie

You can also buy 1/8" hardware cloth, but it's harder to find than 1/4" and 1/2".

If you want to make a wooden frame, try using cedar fence boards. When they're dry (cured), they're quite a bit lighter than pine or fir, etc.

Also consider trying different brands of peat moss. Some are full of sticks and chunks, some are quite well sifted as it comes out of the bag.

Sue

I started out with screen stapled to a picture frame. In my garage sale travels this summer I spied a cutting board/strainer. It was intended for over the sink veggies to drain. I threw the board away and the strainer works great. It has supports so will last forever. She was so excited, thought I would love it! I didn't have the heart to tell her that the board was so nasty it would not go in my kitchen and the strainer would be great for peat or sand. Kathy