A common problem with real estate agents is that they really want to close deals so their advice is often biased. For impartial advice is best to ask friends, family and possibly also try some internet forums.
Carfax
The product's label
The product's label
The product's label
You can find a reliable source for buying glass for picture frames at specialty framing stores, art supply stores, or online retailers that specialize in framing materials. Be sure to look for stores with good customer reviews and a reputation for quality products.
You can find a reliable source for buying a used road bike at reputable bike shops, online marketplaces like eBay or Craigslist, or specialized cycling forums and websites. Be sure to thoroughly research the seller and inspect the bike before making a purchase.
There are plenty of places online that will give you advice and help on your love life. Try Elle or Glamour Magazine, both these sites have experts who supply advice on relationships, sex, and love.
Kiplinger has reliable info on buying foreign bonds directly. This is a very complicated thing to do though.
Any car stereo installation merchant is a reliable source for buying and installing your car alarm.
You can find reliable sources for buying out-of-print books at online marketplaces like AbeBooks, Alibris, and BookFinder. These websites specialize in rare and hard-to-find books, offering a wide selection from various sellers around the world.
The product's label
Reliable is an adjective, and source is a noun.