Here are some basic examples of typical pivot modulations in simple piano music. They all offer simple harmonic models for moving from tonic to dominant major (e.g. C major to G major).

Alternatively, here are some nice simple transitions for string quartet (e.g. thirds and sixths)

There are also some more complicated modulation models for string quartet on this page.

1) Thema from Mozart Sonata in D (KV. 284)

2) Allegretto from Mozart Sonata in Bb (KV. 333)

3) Allegro from Corelli Trio Sonata in C (Op. 5/3)

4) Moderato from Haydn Divertimento in E major (Hob. XVI: 13)

This features a more abrupt modulation rather than a pivot. The chromatic change in from iib in the tonic to V in the dominant (F# minor to major –  A to A#) is often done without the intervening root position ii.

5) First movement from Haydn Sonata No. 3 in F (Hob. XVI: 23)

This is more complicated, being longer and involving another key in between tonic and dominant.