I bought stainless steel sink strainers off Amazon and I put them over the stand pipe to still allow overflow and prevent grain from getting through. The one I bought came with 2, and I put them both on in a cross pattern.

Also, I'm sure this goes without saying, but be careful when mashing in cause there is a gap between the grain basket and the main unit. I have had a few batches where I accidentally poured some grain between the two and I had a bad time.

Note that with even these preventative measures I still end up with some build up on the pump filter in the bottom by the end of it.

From my Amazon orders: https://www.amazon.com/gp/aw/d/B00FH2PBS2?psc=1&ref=yo_pop_mb_pd_title