You can't really get HFCS as a consumer product. But, you can buy some products, say cheap pancake syrup, that have a high proportion of HFCS in them. (I'm not suggesting pancake syrup for bee food.)
Note that "corn syrup" (one example is Karo corn syrup) is not the same product as
high fructose corn syrup (HFCS). For more info, see the comments under "nutrition" at this
Karo page.
Some Beesource members have reported being able to buy HFCS from local food manufacturers that buy HFCS in large quantities. I have seen references to beverage bottling companies, pickle manufacturers, and bakeries selling HFCS to beekeepers.