Welcome Bonsai.
I do not know what it costs in Japan, but I'd highly recommend the FA 31mm F1.8 Ltd. The cost of this lens is only going to go up and it is a stellar performer. I can also recommend it's two brethren, the FA 43 ltd and the FA 77 ltd. But for landscapes, and general photography, the 31 cannot be beat. Here is a link to a myriad of FA ltd photos, 31mm 43mm and 77mm.
https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/59538-fa-limited-club.html
If you want to go less expensive I would suggest the Tamron 28-75mm F2.8 and/or the previously mentioned Tamron 90mm F2.8 macro. If you get them second hand they should run well under your $800 mark.
BTW there is absolutely nothing wrong with getting second hand lenses, especially if you go to a reputable dealer like KEH.
NaCl(If I had $900 a FA 31 would be mine in a heartbeat)H2O