You got several suggestions, but there are a couple more relatively small species (say leaf length < 20cm). Subenera Aphyllae, Parishianae, and Proboscidioides are one of the smaller groups. But they are more difficult species within Phalaenopsis. In the parentheses, I put the approximate leaf length (most data from
ranwild).
subgenus Aphyllae (the taxonomy within this group is a bit messy now). (Around 10cm):
braceana
hainanensis
honghenensis
minus
stobartiana
taenialis
wilsonii
subgenus Parishianae:
appendiculata (5-6cm)
gibbosa (10-12cm)
lobbii (7-8cm)
malipoense (around 10cm)
parishii (12cm)
subgenus Proboscidioides:
lowii (10-12cm)
Others in alphabetic order:
celebensis (17-19cm)
chibae (12-15cm)
cochlearis (15-20cm)
deliciosa (12-15cm)
equestris (15-30cm plants from Appari are the largest)
fimbriata (15-20cm)
javanica (13-14cm)
lindenii (12-15cm)
lamelligera (12-15cm)
maculata (18-20cm)
mysorensis (2.3-4.6cm)
manii (18-20cm)
micholitzii (12-15cm)
modesta (15-20cm)
sumatrana (18-20cm)