I messed up my observation window when applying Tung Oil and wanted to order another piece. Measured the dimensions and posting it up in case anyone finds it useful. Be cautioned, removing dried up tung oil from the acryllic is very difficult 
Width: 4 3/4 inch
Length: 10 3/4 inch
Thickness: 1/16 inch
Corner Radius: 1/2 inch
Good note for others to learn from. Sorry you had to learn the hard way. Tung oil can be very sticky n damaging to plastic windows. It’s probably best to oil first several layers then install the windows. I know others have written notes on this earlier here on the forum. Thanks for the note for others to learn from ! Gerald
Hey,
i had the same problem with the Tung Oil. After several trial and errors i used orange oil cleaner, just pure on an old cloth and its all gone.
In that case, citrus solvent (D-Limonene) should work too, as that is the active ingredient in orange oil cleaner. Good to know, thank you! 
If you truly have bollixed it up I suggest that you trace a pattern around the window plate and take it to a plastic shop and have one cut. Shouldn’t be more than maybe $10. Tap Plastics has a corner on the market in the US, but I am sure you can find someone who cuts acrylic.
I hope the citrus solvent works!
I tried to clean it myself with some super strength hand soap I had laying around and it ruined the window 
. It looks all foggy now. Will look for a shop - thanks all!
Had you peeled off the plastic film? I am hoping that maybe you just scratched that, because it is very soft. It is hard to see, but there is a layer on the window that protects it in shipping. You might be able to just peel it off now, and everything will be fine?
Yup, had peeled it off. I found a plastic shop nearby so will be checking it out this weekend - seems like it won’t be that expensive to get a replacement luckily!