Auto stores sell battery hold-down devices of many different shapes and configurations. Browse your local auto stores and if nothing jumps out at you for your need there's always
Amazon and other web stores.
You are right; very few chassis parts are custom-made by MH mfgrs. unless we get into Foretravel, Prevost, Newell, and other such MH's.
__________________
2000 Winnebago Ultimate Freedom USQ40JD, ISC 8.3 Cummins 350, Spartan MM Chassis. USA 1SG, retired;PPA,Good Sam Life member,FMCA.
"We the people are the rightful masters of both the Congress and the Courts - not to overthrow the Constitution but to overthrow men who pervert the Constitution." Abraham Lincoln