[sdiy] OT? MIDI to RS232 converter box?

[MTG]

I'm looking to BUY a "simple" converter box that takes 5-pin DIN MIDI at 
one end and on the other true DB-9 serial (at say 38.4kbaud). So this 
would entail a microcontroller with a couple of circular buffers and 2 
UARTs. NOT just a level-shifter-to-current-loop thing.

I don't really want to build it from scratch if I don't have to. I don't 
want any other intelligence, but other baud rates and/or USB virtual 
serial would be fine. All I can see online is a $600 box and a bunch of 
etch-your-own board PIC kits. Oh and some DMX ones, but not sure about them.

Reason: to run an old EPROM monitor in an old synth. The monitor 
utilizes the existing physical layer of 5-pin DIN MIDI, but on the host 
side the monitor is operated via a COM Port Terminal program like TeraTerm.

I would have thought there were at least some old half-baked solutions 
for people that didn't want to pony up the big bucks for a MPU-401.