I would suggest buying L3+ directly from Bitmain. They will likely post a new batch shipping in October.
Don't waste your time and money buying L3+ 's for 5000 USD plus. You will never ROI under 1 year with the rising difficulty. Instead, take 50% of your budget and buy Litecoin LTC right now at market price. Put some orders at $35 they may get filled on the dip.
Also don't rush into any L3+ deal that seems too good, here in Litecoin forum, on eBay or Amazon. Be very careful who you are dealing with, even if it seems a legit seller on eBay or Amazon with 100% positive feedback. Factor in you will pay $150-200 for shipping plus border tax. Depending where you are broker services, plus customs clearance & border tax may be 25% or more of L3+ value.
Wait for Bitmain to post a new batch, or contact Innosilicon and see if they got anything available for September / October. However, Innosilicon Dominator A4 is half the speed of L3+ and more expensive. DO NOT BUY from ANY SO CALLED RE-SELLERS there is a really good chance you will get scammed of your $ and you will never see the miner.
Buy LTC now. Take 50% of your $ budget and buy LTC Litecoin at market price.
Wait for next available batch of L3+ & Buy only from Bitmain. There are no official resellers for Bitmain or Innosilicon.
Beware of any L3+ offers that seem too good to be true. (available stock from so called "resellers", deals for multiple units, discounts for money orders, etc.)