I just ordered 2 of these Tempress hatches. I've heard good things about them and they come in different sizes. Search "hatch" on cabelas.com
Model number is just like the Jon boats. It's the size of the hatch. I bought Tempress 1317 which is 13"x17" and installs into a cutout of 10 5/8" x 14 1/2"
https://www.cabelas.com/product/Tempress174-1317-Access-Hatch-with-Cam-Latch/737552.uts?Ntk=AllProducts&searchPath=%2Fcatalog%2Fsearch.cmd%3Fform_state%3DsearchForm%26N%3D0%26fsch%3Dtrue%26Ntk%3DAllProducts%26Ntt%3DHatch%26x%3D0%26y%3D0%26WTz_l%3DHeader%253BSearch-All%2BProducts&Ntt=Hatch&WTz_l=Header%3BSearch-All+Products