You can email support https://help.market.envato.com/hc/en-us/requests/new and see if they are able to help but historically this has not been an option.
Just for reference you can transfer the license i.e. the license to ‘use’ the item from your developer to you. It’s only the support and download of updates etc. that can’t be migrated.
For what it is worth I agree it’s not convenient. Although I see zero reason why a developer would buy an item and not have the client do it (unless they are planning on misleading them). But at the same tie I completely see why Envato do it - regardless of how honest most situations are, the ability to do this would open up opportunities for less genuine cases to exploit it.
It’s also the same on other marketplaces and not an exclusive issue here, and I suppose (having bought more items than most people here) , if it’s not a policy anyone is happy with then we shouldn’t agree to the T&Cs when signing up/buying