some searching brought up a old amiga.org thread with some links like:
http://www.megaupload.com/?d=961EHGR6
then the newtek FTP
ftp://ftp.newtek.com/pub/Patches/Flyer/
Look around the ftp 4.3 might be there but i doubt it.I think i saw 4.2 there.The floppy installer disk for sure(which i think needs to be high density).
you will probabaly find more video toaster users on amiga.org and might try asking there.
supposedly 4.3 is still available new from Newtek.com
hope this helps a bit.
mech