There are R12 "replacements" on the market. I understand that they are explosive. At first thought, this may not sound very bad, after all, it's sealed up in a refrigeration system. Consider this, what if a spark were generated by a compressor failing or locking up?
Living in Texas, I am very aware of the desire for an inexpensive alternative to R12, but as far as I'm concerned, this is not it. If you know you have a tight system, use R12. If you're not sure, it might be time to changeover the system to R134.
'84 Euro 240D, 516K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in