Troll Lord Games

I am running a strong medieval type game of D&D set on the coast of a colonial type setting. Platemail is the most advanced armor you can buy and I kind of thave the Teutonic Knights floating around. Technically the Heldannic Knights from Mystara. I plan on mining Mystara heavily and one of the big bads is a death knight and the C&C DK is weaker than the AD&D one so it may make an appearance soon.

Anyway I am thinking of doing it ye olde dungeonn crawl style but maybe having some lost technology here and there like the Barrier Peaks space craft, techno mages living in hidden cites and maybe even a flying city or something similar powered by magi tech. Most of that stuff will not be available to the PCs of course. Hobgoblins are a bit more organized on my world and they are basically the imperial Roman legions are also hanging around like a bad smell.

Any easy to insert level 5 adventures one can buy?

Excuse me answering your post with a bunch of links; I know you are looking for some curation from our august community, but at least there are lots of choices.

Free:
http://www.dungeonmastering.com/campaig ... adventures
D&D (some available at dndclassics.com)
https://en.wikipedia.org/wiki/List_of_D ... ns_modules
Goodman Games C&C
http://www.goodman-games.com/castlesandcrusades.html

TLG adventures generally tend to be in loose series, so, look for the low/middle part of the series to find modules in your level range. Determining level range is a dark art anyway; as always the CK needs to adjust.

Speaking to your "Hobgoblins are a bit more organized", that is suggestive of the Kingdoms of Kalamar adventures. http://www.rpgnow.com/browse.php?cPath=568 , maybe you'll find something that fits your world there.

Also take a look at the stuff Eldritch Ent is doing, maybe you could run Snakeriders of the Arodondo, Curse of the Weaver Queen, or Lich Dungeon I+II. They use generic stats but are simple to convert to C&C. http://www.rpgnow.com/browse.php?manufacturers_id=4250

If you can work with adventures not designed for C&C I would highly recommend you take a look at Goodman Games' Dungeon Crawl Classics #36: Talons of the Horned King (An Adventure for Character Levels 3-5 ).

This module was designed for the 3.5 D&D rule set but has the space technology concept you are seeking, al la S3 Expedition to the Barrier Peaks.

Here is the link to the modules description: http://www.goodman-games.com/5035preview.html

RPGNow.com sells the .pdf of this module for $9 (it's on sale for $3 right now).