If you want to buy --
Swisher pens Click on the Calligraphy button
Pendemonium Click on Writing Instruments in the left margin and then Dip Pens in the middle array.
Pear Tree Pens Click on Brause in the left margin.
Art shops may have a range of pen holders and nibs.
If you want to make --
Look at some of the examples, particularly in Pendemonium. A holder would seem to me to be simple to turn. The only problem is getting the slot in the front right so it will take standard nibs.
You may have to buy some cheaper holders so you can get the pen slot dimensions.
You may want to consider making a dip nib from a feather. The only real problem there is persuading the goose, swan or ostrich to let you have the raw materials.