International insurance coverage to USA

Hello,
I have my 2 elderly parents travelling from India later this year and will be visiting the USA for about 3 months. I would like both of them to be evaluated by physicians here in the USA for some non-emergent medical needs, a dermatologist and GI specialist to be exact. Has anyone purchased international insurance before in a similar situation? I am looking thorugh the imglobal webiste and predomiantely am seeing Patriot or USA healthcare. challenge is getting pre-exisiting conditions and nonemergent procedures such as a colonoscopy/other imagings covered.
-Thanks in advance!