For HOB filters there really isn't any way to fix it without modding the filter other than raising the water level as much as possible. I ended up having to buy a canister filter with a spray bar to make it safe for my betta.
I used a bottle baffle, works like a charm, super easy to make and doesn't really modify the filter
Sorry - I should have posted a link. This article explains how to make one. It's basically a plastic water bottle with the top and bottom cut off and a slit along one side, clipped over the outflow part of the HOB. It fits nicely on my Aquaclear, not sure if it will work for all HOBs. I attached mine with a single cable tie through a little hole in the top.
Step-By-Step Filter Baffle
I made one of these and it works like a charm! Thanks again!