Yeah i had the same issue with trying to get a speaker for the Hp1.Scanner master has a lapel speaker made by spectrum force in the speaker section of their website,I bought one for my 396 xt and it sucks it's very low with the scanner volume turned up all the way
I ordered one of these. As soon as the holiday and all this snow gets behind I hope to receive it. I will let you know how it does. I attached a pair of Sony ear buds today and audio was loud. Not as clear as 8 would like but works. One thing I know is if this the quality doesn't get better I won't be using any earpiece much unless it's absolutely necessary as after an hour it started to get a little tiring.
Looking at the plug on the picture it appears to be stereoI use a ear piece like this on my HP and just tried it on my 436. It works better on the 436 then the HP. Much louder and clearer. Which is kinda funny since UPman had said to me in another thread to make sure to use a Stereo plug and not the mono plug for headphones as it could damage something in the scanner otherwise. The plug on mine is mono not so sure about the one in the link AZ supplied. Good Luck.