Companies like LRP make rounded LiPo batteries which fit into the round cavity found in older Tamiya bathtub chassis like the TA01, TA02, TA03, CC01, DF01 or FF01. However, compared to NiMH stick packs the LiPo cases are about 5 mm longer. This means that the battery is sticking out too much and the battery holder that comes with the car no longer fits.
We designed a 3D printable holder that solves that issue. For good measure we included a case for the popular 1-8S LiPo monitor -- often those old cars run speed controllers without LiPo cut-off.
A LRP LiPo stick pack in a CC01 chassis with our new holder with included LiPo monitor.