We've put together two mini-collections of monsters for 5e. Most of the monsters appeared in earlier editions of the world's most popular fantasy RPG, but were omitted from the official monster manual.
One collection features five constructs (http://www.rpgnow.com/product/165547/5e-Fiendopedia-Forgotten-Constructs) and the second contains five underground humanoids (http://www.rpgnow.com/product/165548/5e-Fiendopedia-Underground-Humanoids).
They are on sale now for less than $1 each. Let us know if we should make more!
The 5e Fiendopedia is designed to augment the monsters available to a game master. Each monster has its own page, including a wonderful color illustration. Print them out, hole-punch them, and place them in a binder. Keep a binder of just those used in your campaign. Sort them by name, challenge, environment or any other way you need them. More 5e Fiendopedia are forthcoming with even more creatures!
(http://inkwellideas.com/wp-content/uploads/2015/11/underground_humanoids_rpgnow-234x300.jpg)
(http://inkwellideas.com/wp-content/uploads/2015/11/forgotten_constructs_rpgnow-239x300.jpg)