Well, 9mm gives 300X or so and for a refractor...
You could buy a cheap 6” achromatic but that won’t be much good past 100X, you do need premium glass such as an ED doublet something like this...
http://apm-telescopes-englisch.shopg...m/333631363633
But bear in mind this no lightweight and will need a mount - at the minimum an AZEQ6 or G-11. The downside is it’s not much good for DSOs as the aperture is small. The fun begins at 200mm (eg a C8).
Alternative along focal length Newtonian(dobsonian), or a schiefspiegler (you will have to build that)... or a 9” maksutov like my MK91 and these are very rare.