If you’re unable to find exactly that, you could also combine a Bluetooth transmitter and a Bluetooth receiver. It may be a little expensive though.

For example, you could get a transmitter such as this Homespot adapter

and then use it with a Bluetooth receiver such as this one. You may be able to find one of these cheaper but this is the one I’ve used before.

Both of these support aptX low latency, which will allow them to have much less lag than what you experienced with your Bluetooth headphones.

Just make sure whatever you buy does support aptX LL if you want to minimize the lag

You could also try the Bluetooth receiver by itself to see if it has less lag than your headphones when connected directly to the Switch. But, the Switch doesn’t support aptX LL, so it will still have some noticeable delay

To make it less complicated of a setup, you can buy Bluetooth receivers that output AUX, such as this one

Also, did you know that you can plug an AUX cable into the Switch itself while docked? Not sure if you just don’t want to do that or not, but that seems like the easiest solution

If this causes a static noise, you would just need a ground loop isolator, which are pretty cheap