If you are looking to keep the "period" look, then I say no. My place is from 1916 & had a gross 1980's reno. I ripped out all the ugly vinyl floor & cheap Sears sink & went with a black hex floor, white subway, dark grey grout on both. Toilet & tub were original, but I got an old "Standard" wall mount sink with chrome legs & towel bars & an antique medicine chest, light fixtures & glass shelving & towel bar off Ebay. My total job...about $5k. Help my tile guy is my neighbor, but those 10, 15, 20k bathrooms were out of the question.

Third vote for getting a professional involved, but i'll still offer my layman's suggestion given that you're just soliciting general ideas at this point. If it was my space, I'd switch the bathroom and the laundry room around, keeping just one of the walls currently enclosing the toilet. Its hard to estimate precise measurements from the drawing, so it may not be feasible, but here's what i mean

Have you tried looking through the Houzz professional's tag or asking the people who have posted the photos that you've seen where they got their cabinet from?

We have a 900x900 shower and it's plenty big enough. Neither of your proposed layouts looks that great, to be perfectly honest, sorry! In the first layout, you could improve it quite a lot by swapping the toilet and vanity (centre the toilet under the window on the bottom right of the picture if possible), and having the shower door on the other wall (beside the door). Then, you could have a towel rail on the wall beside the door (i.e. behind the door when it's open), which would be accessible from the shower but hidden when the door was open. An 800x1200 shower might be a good size for your space. You'd have to choose a toilet that doesn't protrude too far, plus a narrow vanity. With that layout, you could have a long but narrow wall-hung vanity, with a big mirror covering the wall between the windows, which would make the room feel bigger and would give a good amount of storage. Also, you may find this helpful: http://www.houseplanshelper.com/small-bathroom-floor-plans.html?utm_content=buffer4aa20&utm_medium=social&utm_source=facebook.com&utm_campaign=buffer