Not really... It's possible to get something similar by using objc_util though. This way, you can create a ButtonItem that uses a custom view instead of an image/title, and you could add multiple buttons with custom spacing/size to that view...
A Button as a custom view of a ButtonItem doesn't behave completely like a normal ButtonItem with an image though. For example, the touch target of regular ButtonItems is much larger (taps don't need to be as precise).
Anyway, here's a little demo of what I mean. The spacing is very tight in this example, but it's easy to change.
from objc_util import *
v = ui.View(frame=(0, 0, 400, 400), name='Demo')
v.background_color = 'white'
btn_images = [ui.Image.named(n) for n in ['iob:beaker_32', 'iob:beer_32', 'iob:coffee_32']]
btn_container = ui.View(frame=(0, 0, len(btn_images)*32, 44))
for i, img in enumerate(btn_images):
btn = ui.Button(image=img)
btn.frame = (i*32, 0, 32, 44)
btn_item = ui.ButtonItem()
btn_item_objc = ObjCInstance(btn_item)
btn_item_objc.customView = ObjCInstance(btn_container)
v.right_button_items = [btn_item]