I'll be glad to add them to the list for the next update I do, which at this point will be at least 3-6 months away.
I don't have the time to convert more than 500 bass weights to KG, sorry. If you'd like to do the honors, feel free to download the spreadsheet and do so. All but about a half-dozen of the original posts were in US weight, and I have rounded in some cases, so the conversion would add a slight increase in rounding error.
I think it would be much easier for an individual user to use an online conversion tool to run the weights of the instruments they are interested in.