how can i get a free avalon based i2c slave

i'm searching a i2c slave ip core

the oc_i2c_master on open core is sopc readied,but only support i2c master

i2c slave on open core is a standalone i2c slave, hard to connect on avalon bus

[i2c slave]searching result in altera's web support two cores:

di2csb and mtx_avalon_i2c but need a paid for license