R-lipoic acid "stabilized" should have that on the label.

I find Amazon is a good supplier lately, with free shipping at over $25. Their prices can be the lowest online I found, but be careful and read each offering carefully. They can make mistakes.

Many of us use Doctor's Best brand. I use it for my Benfotiamine as well.

Also iherb.com has both and has always been good, accurate and affordable.

Puritan's Pride is also a good affordable source. But they do not have R-lipoic or Benfotiamine yet. I use Puritan's for many things, including my methylcobalamine.

Did you and your Dad get B12 testing? Vit D testing?
Many elderly patients can be low in B12. NIH even recommends all persons over 50 take it in supplement form.

Get your test results, and do not accept "normal" from the doctor as the test ranges that are reported are old and out of date. You should be at 400 or above to be "normal" now. Living in lower ranges can result in nerve damage and considerable pain which over time may be not reversible.