what's a substitute for matzo meal in latke recipe?

We use rice flour in our restaurant to keep the gluten free. It is also a nice light binder!

You can use flour, as Monita suggests. You can also use the starch from the shredded potatoes. As you grate or shred them, (you should alternate onions with potatoes so the latter don't darken), transfer them to a colander set over a bowl (preferably lined with a tea towel). When all are shredded, squeeze them hard to extract all the liquid. (It's nice to return one-half of the potatoes to the food processor bowl, fitted with the steel blade, and whizz them a bit to break them down, then mix back together with the coarser shreds) Remove the colander, drain the liquid that has collected in the bowl, reserving the starch, and scrape up the starch that has collected at the bottom of the bowl; re-add to the potatoes; add the rest of the ingredients. I find the starch makes them crisper (although the addition of a little flour will help them hold together better than starch alone).

I use flour and it works just as well

for cup of matzo meal, crumble 3 standard matzos,each about 10" square (if you have them). Carr's water biscuits (a British cracker) are basically matzos, so you could crumble them. Or use same volume of bread crumbs or flour. But start with less than the recipe call for - say, 3/4 - and check your potato-matzo meal mixture as you go. You want the flour to help bind the whole mixture, not make it too dry or dense. Maybe make a test latke, and if it's too loose add more bread crumbs/flour to the mix.