Thanks, guys, it wound up being easier than I thought.
I did check Home Depot, Lowe's and local hardware
stores, and they had replacement inside-latches, but
it was hard to tell if they would have been perfect
My idea of "perfect" meant not having to drill new
holes, or re-align the inside latch and/or outside
I found a great supplier called Blaine Window Repair,
and I was able to pop in on them while I was in the
Silver Spring, MD area. (They also have a website
http://www.blaine-online.com/b109.htm and an 800#,
1-800-565-4948. Very helpful guys. You can mail them
a part and they'll do their best to match it.)
They sold me an inside latch by Ultra that was a
perfect replacement. Had it installed within 10 min.
of getting home.