Sounds like Apache is your web server. Since you mentioned you can't use regex, here are couple of other suggestions:
You should avoid using .htaccess files completely if you have access to httpd main server config file. Using .htaccess files slows down your Apache http server. Any directive that you can include in a .htaccess file is better set in a Directory block, as it will have the same effect with better performance.
If URLs you are redirecting from/to are too unique, to be matched by patterns, use RewriteMaps, especially DBM Hash File.
When a MapType of dbm is used, the MapSource is a filesystem path to a DBM database file containing key/value pairs to be used in the mapping. This works exactly the same way as the txt map, but is much faster, because a DBM is indexed, whereas a text file is not. This allows more rapid access to the desired key.