Is there a source for frosted LED globe type bulbs for lionel or MTH goose neck lamps

Here's a link to a site that may have them. 

Town and Country

What base are those?

If you can't find one, you might be able to make one by gently breaking the globe off, and gluing it to an LED.

Town and Country  are fantastic.  If they do not have it, you do not need it.

Is this conversion is part of a bigger layout lighting project?  No matter which screw base those goosenecks use you'll generally find more (and less expensive) LED replacement bulbs from the massive 12V DC automotive market than for our tiny specialized 14-18V AC O-gauge market.

Point being, another option is to re-wire your lighting for consistent + and - polarity.  Would still work for AC but would now allow you to switch over to 12V DC operation.  Going 12V DC would allow use of LED lighting strips which are popular for illuminating buildings, station platforms, etc. costing a few pennies per LED. 

Additionally, 12V DC power is readily available from low-cost (less than 10 cents per Watt) wall-warts or brick adapters.  The cost per Watt from the AC-accessory voltage of a train transformer is more expensive...and it typically draws from overall power output of the transformer leaving less power to run trains on the main outputs.  I realize most guys have one or more dedicated AC-output transformers for lighting but you do see the occasional post decrying how accessory AC "steals" from available track power.

Guys, thank you, all great ideas. I did send T&C an email. I didn't see exactly what I was looking for on their site.

Stan, yes this is all new setup so I could set it up as you suggest.  Elliot's suggestion could be used as well with that route.

Hopefully you'll find an off-the-shelf LED bulb, but wrt to Elliot's suggestion

On the left I broke the bulb off a bayonet-style bulb and then soldered two wires.  This allowed me to access track power on a passenger car using the existing socket so I didn't have to alter the original (re-sale value, etc.).  The wires ran to LED lighting electronics.

On the right, I replaced the incandescent bulb that used the press-fit socket with a DIY LED contraption.  In this case I could not find an LED that had this type of socket.  Plus, what you may find is many of the first-generation LED replacement bulbs use just a single LED.  As shown I used 4 LEDs which is, well, 4 times brighter and uses power more efficiently.  There's some annoying do-the-math but ironically (if that's the right word) when you reduce 14-18V AC to the ~3V DC of a single LED, the efficiency is not that much improved by going LED!    That is, we've come to expect huge savings with home light bulbs when going from incandescent to CFL or LED - like "100 Watt equivalent bulb uses only 15 Watts!"   Your mileage may vary.

I haven't seen LED replacements for any of the special shaped bulbs. Probably just a matter of time.