If you can't find kits you might be able to make the correct size
orifice by measuring the orfice you have, getting a replacement
orifice with a small hole and then drill it out to the correct size
determined by orifice charts

these charts might be helpful in figuring it all out

http://www.mobilehomerepair.com/medi...city_Chart.pdf
http://www.joppaglass.com/burner/lowp_chrt.html

cheers
Bob

These charts should be a BIG help with the stove ... not sure about the
water heater, but I SHOULD be able to get a complete NG burner assembly
for that, if one is available.