It's printed in two different publications. "Solos for the Double Bassist
" from Liben, and Nouvelle Technique Vol. 4
from Leduc. The first is an older transcription by Frank Proto, while volume 4 is updated and ostensibly more accurate.
If you don't want to buy it, see if your university participates in the InterLibrary Loan (ILL) service. Normally your library can rent certain titles from other libraries for free if you can find it on WorldCat.