Everyone has their favorite, but the basic question is what can you, personally, afford to buy?
Anyone can buy mil-issued gear from most any country. it will cost you, and it will be tailored to their weapons and tactical dogma. Maybe not yours.
IMHO, the most cost-effective equipment currently available in this country is the very inexpensive milsurp ALICE gear. With some slight, and optional modifications, it will serve you well, and not cost much. It is usually a good value.
As far as dyeing your older vietnam gear, it is probably more valuable to a collector as-is, along with your letter of provenance.
Sell off all the obsolete cotton gear, and upgrade to, at least, late-isue nylon ALICE stuff.
You can go further, if you wish, into ALICE/MOLLE hybrid packs, and into late-issue MOLLE gear, but keep in mind tha t ALICE and MOLLE have a degree of interchangeability, so most ALICe gear you buy can still work if you upgrade to MOLLE.
See the ALICE threads, both in survival gear forum, and in tactical gear forum on this site. Those threads will answer a lot of questions.