The F-20 and F-16-79 were developed for the export market in Carter's time, who had maintained restrictions on the technology the US could export. This was lifted during Reagan's time, at which point, countries wanted the F-16-proper - basically leaving the F-20 and F-16-79 to wither.
IMO it'd be wise for Bangladesh to avoid Russian planes all together. I know the MiG-35 and Su-30SME are solid platforms, but you're not just buying the fighter, but the after-sale support, training and logistics packages. The Russians have every incentive - especially as a probable credit/loan-source - to tie Bangladesh to the Russian industry for spare parts, MRO, etc. Sure, I think one could try pushing the Russians to open up shop in Bangladesh by investing in the local MRO base and manufacturing parts under the UAC brand (but in BD), but that's no guarantee for war-time security (as Moscow can ask UAC-BD to stop or recall critical staff). There's also the risk of tying one's budding aviation industry to foreign ownership - e.g. capital outflows from profit, inability to control pricing domestically, etc.
The alternative (if not JF-17/FC-1) should be the JAS-39C/D or E/F or the J-10A (or if possible J-10C, though AVIC hasn't put it up for export). The JAS-39E/F's all-in costs (i.e. flyaway cost plus after-sale support etc) is around $130-150 m per jet, which is the lowest of the Western fighters. Sweden is also willing to release loans for sales.
Avoid local assembly, push for stockpiling as many spare parts and spare engines as possible and aim for domestic overhauling. Once you finish paying for the purchase, leverage a follow-on purchase to having Saab outsource some parts manufacturing work for all Gripen (or other products) to Bangladesh.