Would have thought that any decent Stockbroker could facilitate this, they're all done thru Euroclear.
Note that the Turkish Govt is BB- and issues paper in both USD and TRL, it's obviously the latter that's gonna provide the yield eg the 14% of Sep 12 are trading 97.20 ish to yield a short 16%.
Yoo also have some AAA paper issued by people like the EIB (European Investment Bank) and Rabobank. This is TRL denoiminated and will yield less that the equiv Govt paper because of the rating improvement. eg IBRD 13.625 of May 17 currently 99.25-100.10.
It's a pretty well developed retail market, shout if more info required.