I did a DIY to my TT for the fresh drain tank for around $25.
Go to Home Improvement Center for items.
Brass drain plug with 1/2" nipple.
Quarter(1/4)turn, 1/2" inline valve.(this is a valve you can attach pipe on each side).
1/2" 90* brass elbow.
1/2" plastic pipe of your choice.
Screw Clamps to attach pipe
Large Zip Ties to tie things up around TT frame to hold pipe in place to not let sag.
I used brass components as it won't rust over time and components used, had barbed(serrated) ends for leak proof connections.
Now for the drain pipe, I used 1/2" PEX Pipe(easy to cut/strong) to attach all the components. I was lucky as my BIL had the crimping tool and tubing rings to give a clean result. I used no more than 18" of PEX pipe. Kept drain pipe under TT for hidden looks, but easy reach of drain valve from side of camper. Tank drains under axles of TT.
One thing you have to do is do a "FIT" of components before clamping down in permanent position.
You can use many, softer, 1/2" pipes available, and you'll need some screw clamps, and for the tubing, you'll need what length you decide on, how and where you run the drain pipe to.
I don't have pictures at this time, sorry.