A number of websites provide rehearsal aids to help you practise your part. Below are some free or reasonably priced ones. You can bookmark them / add to favourites (or download in the case of John Fletcher), to avoid having to come back here each time.
Here are links to Poulenc's Gloria and Bernstein's Chichester Psalms on Cyberbass.
Here are links to Poulenc's Gloria and Bernstein's Chichester Psalms on John Fletcher Music.
Both works are in copyright and so you will need a premium plan (starts at $4.40 for 4 months) to access these files.
'Click here for the sound files', then the movement name, and then the mp3 file for your part (ignore any files ending in .sib, .mid or .mxl - you only need the files ending in .mp3) and click the play arrow.
On a computer you can also right click on the mp3 file and download it, so that next time you can just click on the file on your computer. The files are stored on an unwieldy site called Dropbox; ignore all offers to try/join/signup/copy to Dropbox as you don't need to - just 'continue to download'.
Best for: downloading files so you can play them offline, load them onto a phone/mp3 player, or write them to a CD. (You can also play them online but it's fiddly to navigate to the files each time.)
YouTube
Many of the more popular works have rehearsal aids (and performances) on Youtube. Use your preferred search engine to search for the name of the piece + rehearsal aids + youtube to find one that you like .