tRNA expression system/plasmid for yeast

[Josmar]

Dear all,
as this is probably a stupid question to ask, please forgive me my
ignorance. Is there anything like a tRNA expression plasmid for yeast?
We would like to use some kind of RNA carrier molecule to "present"
aptamers, mainly to protect it against rapid degradation. We recently
designed a SELEX library with a, what we think, stable stem
constraint. Embedded in this stem is an RE site to directionally clone
enriched libraries into any carrier molecule that, as a prerequisite,
must contain an identical stem. The idea is to minimally disturb/alter
structures of both, aptamers and carrier molecule. A tRNA is the first
type of molecule that comes to one's mind to have defined stems and a
very well defined structure after all. Any kind of input is
appreciated!
Thanks
Josmar