Support de projecteur pour ordinateur portable - Conception métallique réglable, plateau de 20"x16"

I am interested in the Universal Laptop Device Stand PLPTS3X2. Is there anywhere in Australia I could buy one of these? If not how much would it cost to ship to Australia?

You can try to check on ebay.com

https://www.ebay.com/itm/264781178524?epid=22039845599&hash=item3da630269c:g:h8cAAOSwf3xe-7g9

The knob for height adjust does not screw into anything. This stand is useless to me like this. Am I missing something?

Please contact us through our email support system to further assist you. Simply Go to pyleusa.com click on the CONNECT tab then on the drop-down choose Contact Us. Fill out the form and in the last part, you will have an option to write your Subject, and also on the comment box, you can write your concern about the product. Please allow at least 12 to 24 hours for someone to get back to you. You can also contact our support hotline at 718-535-1800 ext 2 during weekdays from 9 am to 6 pm EST.

I purchased 1 of these many moons ago and recently got around to using it. Is it possible to get some parts I've misplaced?

Unfortunately, parts are not yet available.

Do you sell after market parts for this laptop stand. The knob and washer on the main height adjustment on mine is stripped (no longer tightens at all. Need those pieces replaced

KNobs and washers are not available for replacement.

Do you have an Australian distributor? If not do you post to Australia! If you do could you please tell me how much.

Shipments are strictly within US only. But you can try Amazon or eBay for international shipping

The extension leg clamp doesn’t stay fixed: the clamp doesn’t tighten and the table top drops down. It worked for a while and stayed in a fixed position. How do we fix this?

https://pyleusa.com/pages/search-results-page?q=PLPW6D

PLPTS3X2 Is this item actually two stands, and if so how can I buy them in the USA?

Yes they are 2 

https://pyleusa.com/products/plpts3x2