The LAST SESSIONS recordings (5-LP's) with Studs Turkel interviewing &
Broonzy talking and singing was released as a 3-CD box (The Big Bill Broonzy Story) a while ago, and is available on the secondary market:
for example at Amazon:
http://www.amazon.com/Bill-Broonzy-Story-Big/dp/B00000JWNM
and others.

Broonzy info at these sites:
http://www.culturalequity.org/alanlomax/ce_alanlomax_profile_broonzy.php
http://en.wikipedia.org/wiki/Big_Bill_Broonzy
http://www.broonzy.com/
http://www.keeponliving.at/artist/big_bill_broonzy.html

lots more - try google.

Best wishes, Thomas.