Battery Toppers

OK, I'm trying to get info on using a battery topper for a 69 GTX. I'm getting different signals. I know that a topper is lightly wider and that the battery holder probably won't fit.

Is www.batterytoppers.com/ the only vendor of these toppers?

Can I get a battery at Walmart or Costco that will fit under the topper?

Will I need the post extenders?

..you can bend a "Z" style battery strap to fit..('68,'69?)
..the '70 straight style is not wide enough,you'll have to make a new one about a 1/2" wider
..there are standard top post batteries that fit fine.

waste of time

Not sure the Q but when I worked in a tune up shop at least half if not more of the batteries that ended up needing replacement were unsecured in the box & the flopping around/vibration over time killed them