There are a LOT of directors and production monitors on the market, but not one that has 4K UHD resolution, a sturdy build and inexpensive like the Lilliput 4K BM150 monitor. Available at B&H Photo: http://bhpho.to/2d62APN (more links below):
Available in 23" LILLIPUT BM2304K
http://bhpho.to/2dazuz2
Available in 28" LILLIPUT BM2804K
http://bhpho.to/2drHahu
Kupo Monitor Mount (holds up to 17.6 lbs)
http://bhpho.to/2cwBhlS
Kupo CStand (holds up to 22lbs)
http://bhpho.to/2cU9zhc