Would you believe I actually got all 4 of the ones you names plus Starship Troopers a replacement of my Citizen fo the Galaxy and 5 more adult Heinlein's for me to keep on ebay for $2.50 + reasonable shipping!!! It had to be God!!! Total for all 11 old paperbacks was $5.50!!! Heck, you just can't beat that!!!
on the internet (via P2P that shall remain nameless) there are downloadable versions of almost all.