I bought those some 3-4 years ago off of ebay. Some key words were "indigo," "reverse glow," etc.
Here's an example thats closest to what I have:
http://cgi.ebay.com/ebaymotors/i763-86-92-TOYOTA-SUPRA-Non-TURBO-WHITE-GLOW-GAUGES_W0QQcmdZViewItemQQcategoryZ43952QQihZ020QQitemZ300245328542QQrdZ1QQsspagenameZWDVW
Although that is for N/As. You are unlikely to find the exact ones that I have, but ones like in that link are the same design layout. Just search for "Supra gauges."
Here's an example thats closest to what I have:
http://cgi.ebay.com/ebaymotors/i763-86-92-TOYOTA-SUPRA-Non-TURBO-WHITE-GLOW-GAUGES_W0QQcmdZViewItemQQcategoryZ43952QQihZ020QQitemZ300245328542QQrdZ1QQsspagenameZWDVW
Although that is for N/As. You are unlikely to find the exact ones that I have, but ones like in that link are the same design layout. Just search for "Supra gauges."