In our line of work a sealer does not polish the stone. It seals and protects it, but does not cause it to shine. Any sealer that gives a shine is only a temporary fix. You should polish the stone with a stone polish like Diaglo. Here is the link:
http://www.defusco.com/diaglo-marble-1qt-p-1455.htmlUse this product with water to form a paste and buff the stone until you have the desired gloss. Depending on the area you are working on you can use a felt wheel on a grinder or a janitor's buffing machine.
Once you have the desired gloss level, wash thoroughly and allow to dry, then seal it with either Hydrex (if you want an invisible sealer) or with Ager (if you want a color enhancing sealer). If you choose Ager buff it again after sealing it as it is a resin based sealer and will give your stone a permanent "wet" look (think of you sidewalk, then think of the same sidewalk 20 minutes after it stops raining...a deeper darker richer color. Although travertine won't darken as much as a concrete sidewalk does, I think you get the idea).
Here is the link for Ager:
http://www.defusco.com/ager-liter-p-1437.htmlHere is the link for Hydrex
http://www.defusco.com/tenax-impregnator-and-sealer-liter-p-2095.htmlGlad to be of service,
Mark