Reddit mentions of Pilot Iro-Ai Fine-Nib Transparent Blue Body Fountain Pen (FPRN-350R-TLF)

The $25-30 Preras are usually the full color japanese that don't come with the converter. The ~$56 ones are the american demonstrators with converters. Although, it looks like you can pick them up for around $30 now.
Personally I think they're a lot better than the metro, the solid brass body is just too heavy and the center of mass is low enough on the Prera that it can be posted comfortably.

The Eco is the cheapest piston filler but there's other demos that are in the same ballpark in looks. IMO the Nemosine is the nearest.

Nemosine demo $15

Noodlers Demos $23

Pilot Pera $30

You cannot buy Pilot nibs separately, but the Kakuno steel nibs are interchangeable with those on the Metro, Plumix, Prera, Penmanship and 78g. The nibs and feeds are simple friction fit so just grip the nib and feed and pull. The first time you do it they may be in quite firmly, so a very slight twist as you pull can loosen it up.

I would recommend a Prera if you don't like the look of the Metropolitan. In my opinion, a better balanced pen with a far more comfortable section. The demonstrator versions look modern.

I would second looking into the Pilot Prera. On amazon they are about $30 bucks and they look pretty to me! I have a metro that I love, and a Pilot Prera will be my 5th pen :)

You can also interchange nibs between the Prera and Metro. The Prera's Con-50 converter will fit your metro as well! I see it as the metro's demonstrator cousin.

Amazon Link

I would suggest the Nemosine Singularity and save the rest for ink.

The Monteverde Artista Crystal is also very nice (and sturdy).

The Kaweco Ice Sport is a good pen as well - the sub-par converter options are a knock against that one though, imho.

The Pilot Prera is a solid choice, but I feel you get more pen for the money with the above pens (even though I love Pilot pens).

Any of the TWSBI pens should treat you well - I have enjoyed all of them.