Many hobby shops stock pin vises and either assorted drill bits or even drill indexes. Personally I have 4 pin vises (great for holding figures) and a drill index which has bits ranging from #61-80 (.039"-.0135"). With these items, a steady hand and some patience you can drill out tracks, barrels, etc.
Lee Valley Tools has the best price I have seen to date for a drill index. You can find simplier and less expensive Pin vises.