I think there is a fundamental misconception here. The 123 allows US to supply us but does not "require" us to buy from US alone.
Only with 123 can we get the US support for NSG, IAEA clearances from other countries. Once it is there - we can buy from Russia, France, UK and anyone else including China.
A question - If the Left is so opposed to 123 and US, why don't they get India nuclear technology from their comrades in China? China today consumes more than 3 times nuclear energy then India (per-capita basis). Why can't they share it with us Indians ? :)
If Comrade Karat can get us nuclear fuel and technology from China without any conditions attached , he will be a true Indian patriot and Leader