(FORTUNE Small Business) – After 28 years, David Tartikoff's two-person insurance agency, David Tartikoff Services, in Sarasota, Fla., is comfortably profitable and "practically runs itself." That leaves Tartikoff, who admits to being in his "early 60s," with enough time to manage his investment portfolio—which is heavily weighted toward bonds. "I'm concerned with capital preservation and generating income rather than appreciation," he says. Tartikoff takes the same hands-on approach to monitoring his bond investments as he did toward building his business, typically executing between two and ten trades of $20,000 or more each month. During more than a decade of bond investing, Tartikoff has worked with full-service brokers, but he now handles most of his trades through a website called Shop4Bonds.com. The fledgling outfit was co-founded by James Korth and Michael Puch of Miami-based J.W. Korth, a firm that has sold bonds to retail investors since 1982.

Online bond trading has never approached the popularity or convenience of stock trading, even though the $23 trillion market for bonds is nearly twice the size of the U.S. equities market. Many online brokers, including E*Trade, Fidelity, and Schwab, offer a basic menu of 5,000 to 8,000 investment-grade bonds. However, the vast majority of the bonds on those sites still trade through human brokers. And because only a tiny portion of bonds are listed on the New York Stock Exchange—most are traded directly between dealers—you never know how much of a markup you are being charged (an issue that has long troubled the SEC). For example, you might pay a $5 commission to purchase a bond, but you wouldn't know that one dealer offered a price of $1,025 while the next offered the same bond for $1,050.

Another limitation is that most online brokers steer investors toward investment-grade bonds (those rated BAA3 or better by Moody's and BBB-- or better by Standard & Poor's). It's harder to find riskier high-yield (or "junk") bonds, which some investors seek out as part of a diversified bond portfolio.

Enter Shop4Bonds.com, which in February started offering retail investors a searchable inventory of more than 25,000 bonds, rated from C to AAA, along with their dealer prices. That information is much closer to what pro traders see every day. Founder James Korth compares buying bonds on his website to buying tools at a big-box warehouse instead of at the local hardware shop. "At the warehouse, everything is self-service unless you ask, prices are 20% less, and there are 40 drills to choose from instead of just three." Shop4Bonds.com also has a vastly simplified commission structure: $5 a bond for the first 25 bonds, and $3 a bond after that, and you never pay a markup.

Industry watchers think it is only a matter of time before pricing transparency improves, as it did in the stock market, and Shop4Bonds.com may be a catalyst for that change. In late September, in fact, Fidelity simplified its fees—now $3 each for muni bonds and $4 for corporates—and started disclosing bond prices on its website, becoming the first major broker to do so.

Shop4Bonds.com says it has opened 300 accounts so far, and some customers such as Tartikoff have been won over by the broad offerings and transparent pricing structure. They also like the ability to execute trades through a live broker for no extra charge. "I'll go online and look at the listings, and I like being able to place an order online," Tartikoff says, "but sometimes when you have $25,000 to $50,000 worth of trades, you like to be able to speak to a human."