Get yourself the CGA to VGA adapter.  Then get yourself one of these:

http://www.ebay.com/itm/Apple-IIGS-Video-Adapter-for-the-GBS-8200-8220-Video-Converter-/131315833189

Just message him, he's very good at making more when needed.  Works great.

I have this exact combination working with my IIgs and my Apple II with digital RGB card.