Need bits for Emgo 2500 impact screwdriver

[bpjr]

Bought my 1970s vintage Emgo 2500 impact screwdriver new (the one in a metal case which looks like the newer model) and it has served me well all these years. Unfortunately I dropped bits in thick underbrush and couldn't find them. To get the job done quickly I bought an HF impact screwdriver and used bits from it. They started bending and shattering immediately on the same jobs the Emgo bits did without flinching all these years. Anyone know what bit brands are good and where to buy them?

Thanks,
bpjr