Hi I'm not Adam but I thought MRX-40 would be a good choice. Article about MRX-40 on ARRL website:http://www.arrl.org/files/file/Technology/pdf/99759.pdf BG2KAJ Ma

HI Sending everything that goes into the audio port is possible though you have to modify the xtal to another freq as F6GWE said. Ma BG2KAJ

Well, I have my HT-1 internal speaker installed but without extra holes opened on the panel or side. The sound would be extremely weak at low volume but good with max volume. Maybe some holes is neede

Wait, I would like one. Maybe just DM you on WeChat?