Matchbox and other small 123s are pretty much non-existant however, Minichamps makes the W123 coupe, sedan and wagon in 1:43 scale:
Revell has a W123 sedan in 1:18 scale:
FWIW, I saw one of these in a toy store in Finland and these are really nicely done. Knowing that they were made in China, I elected to wait until Hong Kong to purchase...they were almost $15 more in HK than Helsinki!!!!
Also, Verem makes a 123 in 1:43...not nearly as well executed.
Here's where to get them:
http://www.minimerc.co.uk