Recharging R12 air conditioning system of older vehicles in Bangkok area

[Tiger Sam]

I need help from other members of the Thai Visa forums.  I have an older Audi with a good working air conditioning system.  It was fully serviced just last year and recharged with R12 refrigerant.  In the past I usually have the system recharged with new R12 refrigerant during the hot summer season.  This time around I am having much difficulty finding a service shop that offers R12 refrigerant to recharge my car's air conditioning system.  Does anyone know where I should go for such service in Bangkok?  I live near Seacon Square on Srinakarin Road, not too far away from Central Bangna Trad Shopping Mall.