If you can't find anything here in town, you can mailorder from lots of places.
Fliskits has a good selection and variety. Balsa Machining Service is a good solid place to get nose cones, but don't forget about 'Sandman' here on TRF for custom balsa jobs and other needs. I have had good success in the past ordering tubes from Totally Tubular but there is another thread currently here on TRF where a bunch of folks have apparently had recent crummy service.
There is a hobby shop up along airport freeway in the mid-cities---I will try to find a name and number for you. The last time I was up there, they had a fair selection of BT and NC stuff as well as some kits and motors.
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Edit: I think I found it again, it is Hobby Maker at 1424 Airport Freeway in Bedford. Should be close to you?
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On the south side of Fort Worth you can get a few things at Old Time Hobbies (south of 820 on Trail Lake about a block) but I don't think it would be worth it for you to drive that far just for their limited selection.
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Edit: Dynasoar made a comment about a Hobby Town in Dallas, and that store may well be a good one. I can tell you that the Hobby Town on south Hulen in south FW has very little rocketry stuff, just a few lowpower kits. I seriously cannot recommend.
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You probably have an easier drive into north Dallas but I have no idea what stores are over there.
If I buy stuff locally, it is usually when someone has a sale (like the 40% off sale at HobLob this week). I buy a bunch of kits, mostly for the NC parts but for some of the rest too. I just spent $70+ today.....